Instability of parasympathetic nerve function evaluated by instantaneous time-frequency analysis in patients with obstructive sleep apnea

The purpose was to determine whether the instability of parasympathetic nerve (PN) function is associated with fragmentation of sleep and the instability can be improved by CPAP treatment in obstructive sleep apnea (OSA). Fifty-three OSA and 50 non-OSA subjects were examined by full-PSG and pulse rate variability (PRV) was recorded simultaneously using a photoplethysmograph and evaluated by instantaneous time-frequency analysis using the complex demodulation method. PN and sympathetic nerve (SN) activity were assessed by the mean high-frequency (HF) amplitude and ratio of low-frequency (LF) and HF amplitude (LF/ HF ratio), respectively. Furthermore, the shift in central frequency (CF) of the main HF peak over time was monitored continuously. The relative times over which the same main HF peak was sustained for at least 20 s and 5 min in total recording time (%HF20s and % HF5min) were considered as markers of PN stability. Twenty-two of 53 patients with OSA also examined under the treatment with continuous positive airway pressure (CPAP). A significant increase in mean LF/ HF ratio and decrease in HF amplitude were observed in severe OSA. Furthermore, both % HF20s and % HF5min were significantly decreased not only in mild-to-moderate OSA but also in severe OSA, and % HF20s was the strongest independent determinant for arousal index. Treatment with CPAP significantly decreased the LH/HF ratio and increased both % HF20s and % HF5min. These findings suggest that the stability of PN function is impaired by arousal due to repeated apnea and hypopnea in OSA, and that CPAP therapy improves SN activity and PN dysfunction.ArticleSLEEP AND BIOLOGICAL RHYTHMS.16(3):323-330(2018)journal articl

Efficacy of tiotropium and indacaterol monotherapy and their combination on dynamic lung hyperinflation in COPD: a random open-label crossover study

Background and objective: The difference in efficacy of long-acting muscarinic antagonists (LAMAs) and long-acting beta(2)-agonists (LABAs) for dynamic lung hyperinflation (DLH) in COPD is unclear. The purpose of this study was to elucidate the difference in efficacy of LAMA and LABA alone and the combination thereof for DLH. Subjects and methods: Thirty stable patients were enrolled and randomly divided into two groups following baseline measurements. One group was treated with 5 mu g tiotropium (Respimat inhaler) for 4 weeks following a 4-week treatment with 150 mu g indacaterol, while the other group was treated with indacaterol for 4 weeks following a 4-week treatment with tiotropium. For both groups, these treatments were followed by a combination of the two drugs for 4 weeks. Pulmonary function tests, including DLH evaluated by metronome-paced incremental hyperventilation and exercise tolerance evaluated by the shuttle-walk test, were performed at the end of each treatment period. Results: In total, 23 patients completed this study. Both tiotropium and indacaterol alone significantly increased forced expiratory volume in 1 second, exercise tolerance, and improved health status. Tiotropium significantly improved DLH, but indacaterol did not. The combination therapy resulted in further improvements in lung function and exercise tolerance, but not in DLH. Conclusion: The efficacy of tiotropium in inhibiting DLH following metronome-paced incremental hyperventilation may be superior to that of 150 mu g indacaterol, although the effects on airflow obstruction were the same, and the combination therapy showed further improvement in airflow obstruction, but not in DLH.ArticleINTERNATIONAL JOURNAL OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE.12:3195-3201(2017)journal articl

Instability of parasympathetic nerve function evaluated by instantaneous time–frequency analysis in patients with obstructive sleep apnea

The purpose was to determine whether the instability of parasympathetic nerve (PN) function is associated with fragmentation of sleep and the instability can be improved by CPAP treatment in obstructive sleep apnea (OSA). Fifty-three OSA and 50 non-OSA subjects were examined by full-PSG and pulse rate variability (PRV) was recorded simultaneously using a photoplethysmograph and evaluated by instantaneous time-frequency analysis using the complex demodulation method. PN and sympathetic nerve (SN) activity were assessed by the mean high-frequency (HF) amplitude and ratio of low-frequency (LF) and HF amplitude (LF/ HF ratio), respectively. Furthermore, the shift in central frequency (CF) of the main HF peak over time was monitored continuously. The relative times over which the same main HF peak was sustained for at least 20 s and 5 min in total recording time (%HF20s and % HF5min) were considered as markers of PN stability. Twenty-two of 53 patients with OSA also examined under the treatment with continuous positive airway pressure (CPAP). A significant increase in mean LF/ HF ratio and decrease in HF amplitude were observed in severe OSA. Furthermore, both % HF20s and % HF5min were significantly decreased not only in mild-to-moderate OSA but also in severe OSA, and % HF20s was the strongest independent determinant for arousal index. Treatment with CPAP significantly decreased the LH/HF ratio and increased both % HF20s and % HF5min. These findings suggest that the stability of PN function is impaired by arousal due to repeated apnea and hypopnea in OSA, and that CPAP therapy improves SN activity and PN dysfunction.ArticleSLEEP AND BIOLOGICAL RHYTHMS.16(3):323-330(2018)journal articl